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electron/shell/common/asar/integrity_digest.mm

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// Copyright (c) 2025 Noah Gregory
// Use of this source code is governed by the MIT license that can be
// found in the LICENSE file.
#include "shell/common/asar/integrity_digest.h"
#include <Foundation/Foundation.h>
#include <array>
#include <cstdint>
#include <span>
#include "base/strings/sys_string_conversions.h"
#include "crypto/hash.h"
namespace asar {
constexpr crypto::hash::HashKind kIntegrityDictionaryHashKind =
crypto::hash::HashKind::kSha256;
constexpr size_t kIntegrityDictionaryDigestSize =
DigestSizeForHashKind(kIntegrityDictionaryHashKind);
constexpr char kIntegrityDictionaryDigestSentinel[] =
"AGbevlPCksUGKNL8TSn7wGmJEuJsXb2A";
struct IntegrityDictionaryDigestSlot {
uint8_t sentinel[sizeof(kIntegrityDictionaryDigestSentinel) - 1];
uint8_t used;
uint8_t version;
uint8_t digest[kIntegrityDictionaryDigestSize];
};
constexpr IntegrityDictionaryDigestSlot MakeDigestSlot(
const char (&sentinel)[33]) {
IntegrityDictionaryDigestSlot slot{};
std::span<uint8_t, 32> slot_sentinel_span(slot.sentinel);
std::copy_n(sentinel, slot_sentinel_span.size(), slot_sentinel_span.begin());
slot.used = false; // to be set at package-time
slot.version = 0; // to be set at package-time
return slot;
}
__attribute__((section("__DATA_CONST,__asar_integrity"), used))
const volatile IntegrityDictionaryDigestSlot kIntegrityDictionaryDigest =
MakeDigestSlot(kIntegrityDictionaryDigestSentinel);
bool IsIntegrityDictionaryValid(NSDictionary* integrity) {
if (kIntegrityDictionaryDigest.used == false)
return true; // No digest to validate against, fail open
if (kIntegrityDictionaryDigest.version != 1)
return false; // Unknown version, fail closed
crypto::hash::Hasher integrity_hasher(kIntegrityDictionaryHashKind);
for (NSString *relative_path_key in
[[integrity allKeys] sortedArrayUsingComparator:^NSComparisonResult(
NSString* s1, NSString* s2) {
return [s1 compare:s2 options:NSLiteralSearch];
}]) {
NSDictionary* file_integrity = [integrity objectForKey:relative_path_key];
NSString* algorithm = [file_integrity objectForKey:@"algorithm"];
NSString* hash = [file_integrity objectForKey:@"hash"];
integrity_hasher.Update(base::SysNSStringToUTF8(relative_path_key));
integrity_hasher.Update(base::SysNSStringToUTF8(algorithm));
integrity_hasher.Update(base::SysNSStringToUTF8(hash));
}
std::array<uint8_t, kIntegrityDictionaryDigestSize> digest;
integrity_hasher.Finish(digest);
if (!std::equal(digest.begin(), digest.end(),
kIntegrityDictionaryDigest.digest)) {
return false;
}
return true;
}
} // namespace asar